Cargo containers are widely used for shipping goods by land, air and sea. These containers are typically large rectangular structures specially designed to be handled and stored in the holds of ships, and on railway flat cars and the like. Further, upon reaching major shipping distribution points, the cargo containers may be adapted for use as trailers used in the trucking industry, so that they may be transported to local distribution points.
These cargo containers typically have caster supports and sill structure at their bottom edges, and are closable by pivoted doors held in closed position by lockrods extending vertically over the doors and into cooperating detents fixed on the surrounding door frame. Lock arms are attached to these lockrods to pivot them about their longitudinal axis for release from the detents, whereby the pivoted doors may be opened. During storage and shipment, these lock arms are locked in closed position by padlocks or the like to prevent pivoting movement of the lockrods and unauthorized access to the contents of the containers.
Unfortunately, theft has become a major problem with such containers because of the manner in which they are used. That is, such containers are frequently left untended for varying periods of time in storage facilities, or even on railway flat cars during transportation from one site to another. Thieves can relatively easily break open the pivoted doors and gain access to the goods inside by using pry bars, hammers, saws and other tools to break the lock on the lock arms, thereby enabling the lockrods to be pivoted to their open position.
Various devices have been developed in the prior art for deterring such theft by making it more difficult to break into the containers. Two examples are shown in U.S. Pat. Nos. 4,372,136 and 4,389,862. In both of these patents, the security lock comprises two J-shaped hasps for hooking engagement over the lockrods in spanning relationship to the doors of the container. A staple on one of the hook members is receivable in one of a plurality of openings in the other to lock the two hasps in assembled relationship on the lockrods so that they cannot be moved apart relative to one another. So long as the lock assembly remains secured in spanning relationship to the cargo doors they cannot be opened, even if the lockrods are disengaged from their detents.
The assemblies in these two patents are adjustable to accommodate different spacing between lockrods, with the increments of adjustment being dependent upon the spacing of slots or grooves in only one of the hook members. Further, the padlocks used to secure the two hook members together are in relatively exposed positions, making it easier to break the lock and gain access to the contents of the cargo container.
In order to reduce the amount of space required for storing and shipping such containers, particularly in the holds of ships and the like, it is essential that the containers be capable of close-fitting relationship with one another. Consequently, it is desirable that nothing be provided on the exterior of the container that protrudes beyond the sill and/or caster support, since any item protruding beyond these extremities on a container can cause damage to an adjoining container when they are being placed or moved in the hold of a ship or other storage facility. Thus, a bulky lock assembly cannot be used that projects beyond the plane of the caster assembly or sill on the container. The two patents mentioned above appear to satisfy this criteria, but fail to solve the additional problems noted.
Accordingly, there is need for a simple and inexpensive security lock that can be used to secure the doors on cargo containers against unauthorized opening movement, wherein the assembly does not project beyond predetermined limits from the container side wall, and wherein the padlock is shielded from access by destructive tools, and a wide range of relatively small increments of adjustment can be obtained to accommodate a wide variety of prior art door constructions.